Add the English messages file

kifu/gtk/messages/en.yaml

@@ -0,0 +1,14 @@
+welcome:
+  content: "Welcome to Kifu"
+hello:
+  parameters:
+    name: string
+  content: "Hello, ${name}"
+games-in-database:
+  parameters:
+    count: count
+  content: |
+    {$count ->
+      [one] There is one game in the database
+      *[other] There are ${count} games in the database
+    }